Playing tunes while using 7th chords are a necessary first step when you're learning jazz piano.
While some beginning jazz pianists want to jump directly to rootless 9th and 13th voicings because they sound more "jazzy," this can be a big mistake. Plain old root position 7th chords are the backbone of jazz harmony and you should play them on the tunes you're learning until they become second nature. Then, once you can play them effortlessly without thinking too much, you can move on to those famous 'A' and 'B' voicings and all the other more advanced stuff.
Here's why: 7th chords are still the foundation of everything that comes after. They remind you of the chord roots in a way that rootless voicings don't as in this sense will keep you in touch with a tune's underlying chord progression, which can be difficult to hear and visualize when you're learning rootless left hand voicings.
This will help you with your walking bass lines too, since the first note in each measure is often the chord root. Playing 7th chords will help your left hand to develop enough muscle memory to automatically go to the root of each chord. This will make walking bass lines much easier for you as you learn new tunes!
They're also vitally important with your soloing, since much of bebop and other jazz involves approaching and landing on chord tones in a specific way. If you visualize the notes of the 7th chord while you solo, you'll always know if you're playing a fundamental tone or an extension/alteration. Even with modal jazz, this is crucial.
So sit down, open your Real Book, and play the melody with your right hand and root position 7th chords with your left. After you can do this, then by all means, go on to walking bass lines, rootless voicings, and everything else you want to learn.
As always, good luck with your playing and remember to enjoy yourself at every step of the way!
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